I checked in FAQ list, no question is appear in it also. How can I repair the fortress? I don't see any 'repair' button.
You can repair fortress, only if it's destoryed. Then fortress is destroyed, you can see the button ''Repair Fortress''.
Then fortress is destroyed, you can't research/build, but you can hire soldiers/workers, you can attack too, then fortress is destroyed.
Then you repair fortress everything backs to normal again. Till it's destroyed again.
Regards, Maeof.